Subsurface prospecting device



` May 9, 1950 J. c. BENDER SUBSURFACE PROSPECTING DEVICE Original Filed Feb. 18, 1936 ATTORNEYS Reinued May 9, 1950 SUBSURFACE PROSPECTING DEVICE John C: Bender, Houston, .lex., assignor, by menne assignments, to Lane-Wells Company, Los Angeles, Calif., a corporation of Delaware Original No.

2,133,776, dated octoberis, 193s,

rial No. 64,484, February 18, 1936. Application for reissue October 4, 1940, Serial No. 359,816

21 Claims. (Cl. 250-83.6)

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification: matter printed in italics indicates the additions made by reissue The invention relates to a subsurface prospecting device which may be employed to detect the location of radio-active formations and particularly where such formations have been penetrated by a well bore so that the instrument may be passed through the formation and in this manner detect the presence of the formation.

In the drilling of wells by the rotary method it is the usual practice to maintain a circulation of slush or mud in the well bore during the drilling operation in order to wall up the sides of the well bore, to exclude water, to prevent caving. to overcome formation pressures encountered, to carry away the cuttings from the drilling bit, and to cool the bit. Needless to say, with deep well bores this column of heavy mud exerts a tremendous pressure upon the formations as they are being penetrated. because the pressure of the static head of the column will approximate thousands of pounds per square inch in a deep well.

This enormous pressure forces water and mud back into the more or less porous formations,

and in many instances a valuable or productive oil or gas sand may be passed unknowingly because of the fact that it has been mudded off by the drilling fluid.

Various devices have been arranged for surveying the well bore, but a majority of these are impracticable because of the fact that in many instances the well casing or pipe of steel has been or is being set in the well bore and the devices are inoperative or inaccurate when in close proximity to such a large body of metal. One class of such devices are those depending upon the magnetic properties of the formation or arrangement of the instrument.

The present invention directs itself to an instrument and method which is entirely independent of the presence of metal and the magnetic properties of the instrument, and relies upon the inherent radio-active characteristics of petroleum and its products.

It is one of the objects of the invention to provide an instrument for locating petroleum sands and other radio-active materials by detecting the location of secondary emissions from such materials.

Another object of the invention is to provide a device which may detect the presence of petroleum sands outside of a well casing in which the instrument is being operated.

Another object of the invention is to supercharge radio-active materials in an earth formation and to thereafter detect secondary emissions from such materials as an indication of the presence of a radio-active material.

Still another object of the invention is to lower into Va well bore in combination a radiant energy discharge device, so as to increase the radioactivity of a radio-active material encountered.

Another object of the invention is to lower a recording apparatus into a well Vbore so as to detect the presence of radio-active materials by determining the [electronic] bombardment against the device when approaching a radioactive material.

Another object of the invention is to lower into a. well bore a radiant energy detecting device so that the radiant energy detected can be recorded or indicated at the surface of the well bore as an indication of the presence and magnitude of a radiant energy formation.

A still further object of the invention is to 'energize a normally dormant radio-active material in a well bore and to then determine the extent of the formation by determining the amount of energy secondary emission therefrom.

Other and further objects of the invention will be readily apparent when the following description is considered in connection with the accompanying drawing wherein:

Fig. 1 is a transverse sectional view of an earth formation which has been penetrated by a well bore, and in which a radio-active formation has been covered by the well casing and which formation is to be detected by the present invention.

Fig. 2 is a vertical sectional view through one type of instrument which may be used for practicing the invention.

The earth formation generally is indicated at 2 and this formation has been penetrated by a well bore 3 and the well bore has been closed off by a metal well casing or string of pipe 4.

A radio-active formation is indicated generally at 5 and may be' illustrative of a petroleum, oil, or gas sand. As previously pointed out, such productive formations as the sand 5 are very often present in the drilling operation' because of the presence of mud in the well and after the casing such as I has been set in position it has been impossible to detect the presence of such a. formation with known surveying or prospecting devices. The present invention has a particular application to the surveying of wells which already contain a steel casing such as l, or it may be readily applied to formations in which no casing has been set, or it may be used in any other desired manner which may be employed in detecting the presence of a radio-active formation The instrument is illustrated generally at Il and may be lowered or raised in the well bore by means of a cable il. This cable is carried by a reel i2 which may be operated by any suitable power mechanism. In Fig. 1 the reel is shown as supported on a standard Il by a shaft Il and an electric circuit Il is shown as being connected to the shaft I4, and it is intended that the cable Il may extend through the shaft to this circuit Il so that indications or recordings of the phenomena occuring in the well may be transmitted to the surface. A recording or indicating instrument is shown generally at Il and is grounded at II. The instrument Il may be a cathode ray oscillograph.

It is intended that the instrument may be 'incorporated in a housing such as Il in Fig. 2,

which may be formed with a lower closure cap 2| and an upper closure cap 22. Various instruments can be in this manner enclosed in a water-tight compartment. The parts of the cable il are shown as passing through the cap I2 to which they are anchored by the support 2l while the stuillng box or gland 2l forms a seal about the cable and prevents the entrance of foreign matter to the housing [|01 In practicing the invention it is intended that the radio-active material to be detected will be super-charged or energized so that it [by primary radiations which may be supplied from natural substances such as radium or uranium, or from artificial sources such at X-ray tubes, whereby such material] may have suiilcient activity that its presence can be determined. To supercharge or energize the formation an X-ray tube has been positioned in the housing 2l and is suitably supported and shielded by a lead Jacket 3l. The anode 82 and the cathode Il of this X-ray tube are energized by an electric circuit indicated generally at Il. A shield or lead cylinder Il extends from the jacket 3i to the side of the housing 2l so that all of the radiant energy from the tube will be discharged in one direction through the cylinder 3l.

A window or port 3i is provided in the wall of the housing 20 and this port may be of aluminum or other suitable material through which the primary radiations l1 of radiant energy may be discharged.

The electric circuit which energizes the X-ray tube I0 may include a -battery 3l and a vibrator type high voltage transformer I9 so that the X-ray tube may be properly operated. The primary is shown as grounded to the case 2l, while the high voltage secondary winding of the transformer is connected to the anode I2, and the lament secondary of the transformer is connected to thecathode. The X-ray tube and its circuit is shown in an elementary form, it being contemplated that any conventional X-ray tube and circuit capable of arrangement within the shell 20 [or other conventional source of artificial or natural radiant energy having the requisite propertiesJ may be employed.

A lead shield or partition Il may be provided inside of the housing 2l so that none of the radiant energy from the tube 3B can be discharged upwardly.

When the device is lowered into the well bore the X-ray tube can be energized and there may be a constant discharge of radiant energy while the device is being lowered into the well. Whenever a radio-active material is traversed the pri- 4 mary radiations 81 will tend to supercharge or energize the formation such as l and in this manner the formation will discharge after the passage of the energizing device, a greater intensity of secondary radiations than previously when it was in a more or less dormant state.

The invention contemplates that this increased intensity of radiations may be detected and the detecting portion of the instrument is shown above the partition Il and takes the form of a window 4| which may be made of aluminum or other material which will permit the entrance of the secondary radiations 42 as a means of indicating that a formation has been energized or supercharged by the instrument.

In order to detect the incoming secondary radiations 42 a Geiger Mller [electron] counter has been deposited in the case 2l, and is indicated generally at Il. Counters of this type are well known and are not believedfto require detailed explanation at this point. It may be generally stated, however, that they are capable of counting the bombardment of secondary radiations against the filament I4 as an indication of the volume of radiant energy which has been transmitted into the vicinity adjacent the counter.

In order to shield the device a lead cylinder Il has been provided and a lead lacket 46 encloses the counter I4. The count of the secondary radiations bombardment is obtained by virtue of the circuit 46' [It] which is connected to an ampliiler 41. This amplifier is in turn operated by a battery supply source Il by virtue of the connections 48. The battery at I8 is grounded at il and an electric connection is carried to the surfce through the cable il from this instrumen In operation, as the windowll passes the formation l which has been super-charged or energized by the primary radiations 31, secondary radiations will pass through the window 4I. and the intensity of these radiations may be detected by the indicator I3 and translated into electrical impulses. These impulses are received at the surface and by means of the recording or indicating device Il, in correlation with a measuring means associated with the cable Ii, the location and thicknessof formation giving oil' secondary radiations may be determined.

Also, the intensity of such secondary radiations tends to indicate the productivity of such formation. A recheck may be made by operating the device on its upward trip.

The amplier l1 may take various forms but it has been found that when it is equipped with a General Electric Company tube type F. P. 54 that satisfactory results are obtained.

In some instances only the detector may be used andthe normal radio activity of the formation detected if desired.

While the instruments for energizing the formation and for detecting the amount of energization have here been incorporated in a single instrument. it is to be understood that they may be positioned in separate casings or housings and coupled in spaced relationship if desired. 0r they may be lowered into the well bore in- .dependently of each other so long as the energlzing of the formation occurs in such a manner that it may be detected.

Broadly the invention contemplates a method and apparatus. for detecting the presence of radio-active material in inaccessible locations.

What is claimed is: l. An apparatus for locating substances confronting a well bore by their property of emitting secondary radiations upon being exposed to a. source of primary radiations, comprising: a source of primary radiations adapted to be lowered into a well bore to impress its radiations upon said substances; and a detector of secondary radiations adapted subsequently to pas said substances. f

2. An apparatus for locating substances con'- fronting a well bore by their property' of emitting secondary radiations upon being exposed to a source of primary radiations, comprising: a source of primary radiations adapted to be lowered into a well bore to impress its radiations upon said substances; a detector of secondary radiations adapted subsequently to pass said substances and translate secondary radiations therefrom into electrical impulses; means for transmitting said impulses to a point externally of the well bore; means for measuring the position of said detector; and a recorder responsive to said means for noting the position, extent and intensity of said secondary radiations.

3. An apparatus for prospecting in a cased bore hole to locate substances positioned behind the casing by means of their property of emitting secondary radiations upon being exposed to primary radiations, comprising: an emitter of casing penetrating radiations adapted to be lowered into said bore hole casing; and a detector also adapted to be lowered into said casing for absorb ing secondary radiations returned from said substances through'said casing.

4. An apparatus for prospecting in a cased bore hole to locate substances positioned behind the casing by means of their property of emitting secondary radiations upon being exposed to primary radiations, comprising: an emitter of casing penetrating radiations adapted to be lowered into said bore hole casing: a detector also adapted to be lowered into said casing for absorbing secondary radiations returned from said substances through said casing, said detector adapted to translate said secondary radiations into electrical impulses; means for transmitting said impulses to a point externally of the well bore; means for measuring the positionof said detector; and a recorder responsive to said means for noting the position, extent and intensity of said secondary radiations.

5. A method of prospecting for substances exhibiting the property of emitting secondary radiations upon being exposed to a source'of primary radiations, characterized by: passing a source of primary radiation in proximity to said substance to permit absorbing of said radiations thereby; then passing a detector of secondary radiations in similar proximity to said substances.

6. A method of prospecting for substances confronting a well bore by their property of emitting secondary radiations upon being exposed to pri. mary radiations, characterized by: lowering a source of primary radiations into the Well bore past said substances; and subsequently passing during the secondary radiating period of said sub` stances a detector of secondary radiations.

7. A method oi' prospecting for substances confronting a well bore by their property of emitting secondary radiations upon being exposed to primary radiations, characterized by: lowering a source of primary radiations into the well bore past said substances; energizing the primary source while traversing said substances subsequently passing during the secondary radiating period of said substances a detector of secondary radiations in the same region previously traversed by said primary source; measuring the position of said detector; and correlating the measurement of the secondary radiations at said region with the vertical depth of said detector to determine the location, extent and quantity of such substances.

8. A method of prospecting in a cased bore hole to locate substances positioned behind the casing by means of their property of emitting secondary radiations upon being exposed to primary radiations, characterized by: discharging casing-penetrating primary radiations into said substances with substantial uniformity by a uniform movement along the casing of a source of such primary radiations; and subsequently, during the period of secondary radiations from said substances, detecting such secondary radiations from said substances as may penetrate into said casing and correlating variations of such secondary radiations with the vertical depth of their occurrence.

9. In an apparatus for investigating formation confronting a well bore wherein the ability of diil'erent formations to emit secondary radiations after being exposed to primary radiations is determined to distinguish the formations from each other: a tool entity carrying an emitter of primary radiations and a detector of secondary radiations and means shielding the detector from the emitter whereby radiations reaching said detector are principally secondary radiations returned to the well borev from the formation; means for moving said tool entity along a well bore; said detector being displaced axially from said emitter to follow the emitter past the formations treated thereby.

10. An apparatus for distinguishing between formations sealed oil' behind a well casing, comprising: a housing structure containing an emitter of primary radiations and detector of secondary radiations displaced axially from said emitter, and shield means minimizing direct transmission of radiations from the emitter to the detector; and means for moving said housing structure along a bore hole while the emitter and detector are in operation. and in such a manner that the detector follows past the formation treated by said emitter immediately thereafter.

11. An apparatus for distinguishing between formations sealed oil' behind a well casing, comprising: a housing structure containing an emitter oi" primary radiations and detector of secondary radiations displaced axially from said emitter, and shield means minimizing direct transmission of radiations from the emitter to the detector; means for moving said yhousing structure along a bore hole while the emitter and detector are in operation, and in such a manner that the detector follows past the formation treated by said emitter immediately thereafter; means for transmitting effects of said secondary radiations on said detector to the mouth of the well; and means for recording such effects in correlation with the position of the detector in the well.

l2. A method of investigating formation confronting a well bore, characterized by: applying at known points along the well bore primary radiations of a character tending to induce secondary radiations from the formation back to the well bore; and immediately detecting such secondary radiations as may return.

13. A method oi' investigating and distinguishing formation which has been isolated by a well level, of continuously transmitting the impulses to a distant point, and there noting their characteristics, thereby obtaining a continuous indication of radioactivity while the survey is in process, the values of radioactive intensity obtained making possible their intercomparison so as to permit the digerentiation between the maf.

terials at one level and those of another.

15, A method of obtaining geological information concerning strata existing within a deep narrow borehole comprising, measuring a radioactive property of the material comprising a stratum in situ at one locality within the borehole, similarly measuring a radioactive property of the material comprising a stratum at another locality within the borehole, the results of the first and second measurements being capable of intercomparison so as to distinguish dierences in geological condition between the materials at the two localities.

16. An apparatus for measuring radioactive intensity within a deep narrow borehole comprising a long narrow holder and a member sensitive to radioactivity, the holder -being mechanically resistant so as to protect the said member, the holder further having a substantial portion thereof relatively transparent to rays from radioactive substances, the said member being so placed relative to the transparent portion of the holder as to cause radioactive rays from substances external to the holder to act upon the said member.

17. An apparatus for measuring the associated radioactivity of substances lining a deep narrow borehole comprising an electrical system adapted to give a series of electrical impulses. means to alter the frequency of the impulses in proportion to the intensity of the radioactivity proximate to the said means, a relay member actuated by the said system and the said means jointly, the electrical system, means, and relay member being held by a single relatively short holder so as to minimize leakage and capacity disturbances in the portion of the circuit connecting the said means and the said relay member, the holder further having narrow lateral dimensions so as to permit its insertion in deep narrow boreholes.

18. An apparatus for measuring radioactivity at inaccessible locations comprising a system employing feeble electric currents. means to alter the frequency of the said feeble currents in proportion to radioactive intensity, a relay means operated by the said feeble currents, a circuit employing relatively intense currents, a conducting member, and indicating means, the feeble currents cooperating withthe relay means to cause pulses of relatively intense current, the conducting member serving to convey the pulses ol inlio f 8 tense current to the indicating means. the conducting member serving lurthr to allow placing the system employing feeble electric currents and the relay means both remote from the indicating means, the relay means and system employing feeble electric currents being placed contiguous to each other so as to minimize disturbing eects.

19. A process for investigating the geological formations traversed by a drill hole, which consists in quantitatively measuring the radio-active properties of the formations encountered at different depths inside the drill hole and determining the variation of the said properties with the depth of the drill hole.

20. The method of geophysical exploration comprising receiving in a drill hole radiations caused by radioactive processes, the said radioactions being transmitted from a limited volume of the formations located at determined depths and adjacent the said drill hole, translating the said radiations into electrical impulses, the number of the said impulses corresponding to the number of the said radiations, measuring the number of the said impulses per unit of time as an index of the strength of the said radiations, repeating said measurements for various other depths of the drill hole and comparing the resulting measurements to thereby determine the vdrioition of the measured radiations with the depth of the drill hole as an index of the varying character of the strata traversed by the drill hole.

21. Apparatus adapted for use in the logging of various geological formations traversed by drill holes. including a sealed casing, an ionization chamber within the casing, the said ionization chamber being adapted to be exposed to radiations caused by radioactive transformations, the said radiations being transmitted from the formations at various depths in the drill hole, means associated' with the said ionization chamber for producing an electrical current when the ionization chamber is exposed to said radiations, means for recording said current, and means for moving :ze said casing in the drill hole past said formans. f

J ORN C. BENDER.

REFERENCES CITED The following references are of record in the me of this patent or the original patent:

UNITED STATES PATENTS' I OTHER REFERENCES "Zeitschrift fur Technische Physik, vol. 26, pp. 196-198 (article by J. B. Ostermeier entitled "Study on the Distribution o1 Radioactive Substances in Deep Bore Ho1es), 1926.

"Canadian Journal ot Research," vol. 11, pp. 652-657 (article by Shrum and Smith), 1934. 

